A stereomicroscope used for, for example, brain surgery takes in a beam for the right eye and a beam for the left eye reflected by a target through an inlet formed at a lower part of a body of the microscope, guides the beams through an objective optical system and a zooming optical system to left and right eyepieces, and enables an optical image of the target to be stereoscopically observed through the eyepieces.
A related art in recent years makes various fluorescent materials (talaporfin sodium, indocyanine green, and the like) collect at a target, irradiates the target with excitation light having wavelengths for the fluorescent materials, photographs fluorescence emanated from the target with a CCD camera through filters, and displays for observation the photographed fluorescence image on a monitor aside from a microscope. Japanese Unexamined Patent Application Publication No. 2004-163413 discloses an apparatus for displaying and observing left and light fluorescence images on a special scope.
A zooming optical system interposed in an optical path deteriorates an image resolution as magnification increases. To avoid this, there is a stereomicroscope that forms, by bypassing the zooming optical path, a high-magnification optical path for providing a high-magnification clear image and switches, as and when required, a normal optical path passing through the zooming optical path to the high-magnification optical path of a fixed high magnification not passing through the zooming optical path. The stereomicroscope of this kind is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2003-195181 that arranges an objective optical system and a zooming optical system in a vertical direction and a high-magnification optical path in parallel with the zooming optical system in the vertical direction.